Rapid deforestation and excessive human intervention into wildlife habitat has lead to frequent straying of wild animals into human habitation. Intrusion into wildlife habitat typically occurs due to illegal encroachment and also when roads, railroads, canals, electric power lines, and pipelines penetrate and divide wildlife habitat. Wild animals attempting to cross roads often find themselves in front of speeding vehicles.
Road mortality has significantly impacted a number of prominent species in the United States and elsewhere, including white-tailed deer, Florida panthers, and black bears. According to a study made in 2005, nearly 1.5 million traffic accidents involving deer occur each year in the United States that cause an estimated $1.1 billion in vehicle damage. In addition, species that are unable to migrate across roads to reach resources such as food, shelter and mates experiences reduced reproductive and survival rates.
One way to minimize human-wildlife conflict is to construct wildlife crossings such as bridges and underpasses that allow animals to cross human-made barriers safely. The first wildlife crossings were constructed in France during the 1950s. Since then, several European countries including the Netherlands, Switzerland, Germany, and France have been using various crossing structures to reduce the conflict between wildlife and roads. In the Netherlands alone there are more than 600 tunnels installed under major and minor roads including the longest "ecoduct" viaduct, near Crailo that runs 800 meters.
Wildlife crossings have also become increasingly common in Canada and the United States. The most recognizable wildlife crossings in the world are found in Banff National Park in Alberta where the national park is bisected by a large commercial road called the Trans-Canada Highway. To reduce to effect of the four lane highway, 24 vegetated overpasses and underpasses were built to ensure habitat connectivity and protect motorists. These passes are used regularly by bears, moose, deer, wolves, elk, and many other species.
In the United States, thousands of wildlife crossings have been built in the past 30 years, including culverts, bridges, and overpasses. These have been used to protect Mountain Goats in Montana, Spotted Salamanders in Massachusetts, Bighorn Sheep in Colorado, Desert Tortoises in California, and endangered Florida Panthers in Florida.
The Netherlands contains an impressive number of wildlife crossings - over 600, that includes both underpasses and ecoducts. The Veluwe, a 1000 square kilometers of woods, heathland and drifting sands, the largest lowland nature area in North Western Europe, contains nine ecoducts, 50 meters wide on average, that are used to shuttle wildlife across highways that transect the Veluwe. The Netherlands also boasts the world's longest ecoduct-wildlife overpass called the Natuurbrug Zanderij Crailo. This massive structure, completed in 2006, is 50 m wide and over 800 m long and spans a railway line, business park, river, roadway, and sports complex.